Soil Survey of Murray and Whitfield Counties, Georgia

148 Soil Survey
Local roads and streets have an all-weather surface and carry automobile and light
truck traffic all year. They have a subgrade of cut or fill soil material; a base of gravel,
crushed rock, or soil material stabilized by lime or cement; and a surface of flexible
material (asphalt), rigid material (concrete), or gravel with a binder. The ratings are
based on the soil properties that affect the ease of excavation and grading and the
traffic-supporting capacity. The properties that affect the ease of excavation and
grading are depth to bedrock or a cemented pan, hardness of bedrock or a cemented
pan, depth to a water table, ponding, flooding, the amount of large stones, and slope.
The properties that affect the traffic-supporting capacity are soil strength (as inferred
from the AASHTO group index number), subsidence, linear extensibility (shrink-swell
potential), the potential for frost action, depth to a water table, and ponding.
Shallow excavations are trenches or holes dug to a maximum depth of 5 or 6 feet
for graves, utility lines, open ditches, or other purposes. The ratings are based on the
soil properties that influence the ease of digging and the resistance to sloughing.
Depth to bedrock or a cemented pan, hardness of bedrock or a cemented pan, the
amount of large stones, and dense layers influence the ease of digging, filling, and
compacting. Depth to the seasonal high water table, flooding, and ponding may restrict
the period when excavations can be made. Slope influences the ease of using
machinery. Soil texture, depth to the water table, and linear extensibility (shrink-swell
potential) influence the resistance to sloughing.
Sanitary Facilities
The table “Sewage Disposal” shows the degree and kind of soil limitations that
affect septic tank absorption fields and sewage lagoons. The ratings are both verbal
and numerical. Rating class terms indicate the extent to which the soils are limited by
all of the soil features that affect these uses. Not limited indicates that the soil has
features that are very favorable for the specified use. Good performance and very low
maintenance can be expected. Somewhat limited indicates that the soil has features
that are moderately favorable for the specified use. The limitations can be overcome or
minimized by special planning, design, or installation. Fair performance and moderate
maintenance can be expected. Very limited indicates that the soil has one or more
features that are unfavorable for the specified use. The limitations generally cannot be
overcome without major soil reclamation, special design, or expensive installation
procedures. Poor performance and high maintenance can be expected.
Numerical ratings in the tables indicate the severity of individual limitations. The
ratings are shown as decimal fractions ranging from 0.01 to 1.00. They indicate
gradations between the point at which a soil feature has the greatest negative impact
on the use (1.00) and the point at which the soil feature is not a limitation (0.00).
Septic tank absorption fields are areas in which effluent from a septic tank is
distributed into the soil through subsurface tiles or perforated pipe. Only that part of the
soil between depths of 24 and 60 inches is evaluated. The ratings are based on the
soil properties that affect absorption of the effluent, construction and maintenance of
the system, and public health. Permeability, depth to a water table, ponding, depth to
bedrock or a cemented pan, and flooding affect absorption of the effluent. Stones and
boulders, ice, and bedrock or a cemented pan interfere with installation. Subsidence
interferes with installation and maintenance. Excessive slope may cause lateral
seepage and surfacing of the effluent in downslope areas.
Some soils are underlain by loose sand and gravel or fractured bedrock at a depth
of less than 4 feet below the distribution lines. In these soils the absorption field may
not adequately filter the effluent, particularly when the system is new. As a result, the
ground water may become contaminated.
Sewage lagoons are shallow ponds constructed to hold sewage while aerobic
bacteria decompose the solid and liquid wastes. Lagoons should have a nearly level